Disk drive units in general are known in the art for use in modern micro computers such as personal and desktop computers. In the most common form, such disk drive units comprise a so called Winchester disk drive having one or more rotatable memory storage disks mounted within a substantially sealed disk drive housing along with one or more related electromagnetic heads for reading and writing data on appropriately prepared surfaces of the disks. A disk drive of this type is sometimes referred to as a hard or a fixed disk drive and is normally available as a compact, complete package with a sealed housing on a rigid chassis or frame together with a circuit board carrying the necessary drive electronics.
Within the sealed disk drive, a rotating constant speed spindle motor is provided for mounting and rotating the disks. Because of the extremely fine tolerances in the internal components of the disk drive, especially the head and disk surfaces, the head-disk assembly is sealed against the outside air to prevent the entry of contaminants. However, it is also necessary to deal with and suppress the sources of contaminants within the disk drive. Currently, a primary source of the problem is that in order to minimize the size of the disk drive, modern spindle motors are designed with many components inside the hub which supports the disks. Typically, adhesives are widely used in spindle motors as a means to retain individual components within the assembly.
Adhesives are typically used in spindle motor to retain components such as bearings, shafts and bores precisely in their relative positions, and to maintain the bearing system in a preloaded condition. Because of the manufacturing sequence for spindle motors, and the difficult environmental conditions in which disk drives are used, the requirements for the adhesive used in the spindle motor are demanding and pose a difficult choice for the user. The adhesive requirements are that it maintain it structural integrity in the motor over temperature cycles which can range from -40.degree. to 70.degree. centigrade. The adhesive must further maintain its structural integrity under significant shocks. In order to avoid contaminating or providing any contaminants to the interior of the sealed disk drive, the adhesive must have a very low out-gasing characteristic.
Furthermore, in order to be consistent with the manufacturing sequence and not unduly delay the assembly of the motors, the adhesive must be capable of both a fast cure and a complete cure so that the spindle motor remains completely clean of any residue. The adhesive must be easy to dispense, and preferably be a single component adhesive. Few practical adhesives are available which satisfy all these requirements. The adhesives that are available are expensive, and the cost of assembly of spindle motors in both process time and tools is high. Therefore, it is highly desirable to replace the use of adhesives with an alternative approach to the final structural assembly of the spindle motor.